Genealogy and The Golden State Killer: Part One

Posted May 7, 2018

As genealogists we're naturally curious creatures. We seek to solve the mysteries in inherent in our work. Of course, gripping enigmas aren't exclusive to genealogy. It isn't surprising, then, when the search for answers can cause seemingly different disciplines to overlap. The Golden State Killer case catches our attention not only because genealogical research features heavily. This fascinating investigation marries traditional family history research with the popular genre of “true crime.”

True crime has become a category of macabre entertainment increasingly favored by the masses with particular focus on serial killers. Much has been written about the most infamous of these: Dahmer, Gacy, Bundy*, et al. People are fascinated with learning the “five w's” with regards to these purveyors of human misery. True crime books*, TV shows and podcasts are wildly popular and the frenzy shows no sign of receding.1

Interest in genealogy has also seen a resurgence due to DNA testing kits* that can tell you a number of things about your ancestry. These tests can connect you with your third cousin, twice removed, as well as a reveal embarrassing family secrets. News articles in recent years are replete with instances of people discovering who they thought was their biological father wasn't, otherwise known as misattributed paternity*, and other shocking and devastating “surprises.”2,3

Enter the newest national serial killer drama.

Joseph James DeAngelo was recently taken into police custody after a more than four-decade-long hunt for a serial rapist and killer who was dubbed The Golden State Killer. DeAngelo is said by law enforcement to have committed approximately 100 burglaries, over fifty rapes and at least a dozen murders across California between 1974 and 1986.4 Cold cases are the law enforcement community's equivalent of a brick wall* in genealogy. The unsolvable issue is examined from all conceivable angles in order to find the answer. When the usual resources are exhausted, new and imaginative approaches are considered.

This wasn't the first instance of modern genealogical techniques being used to crack a cold case. Paul Holes, lead investigator in the Golden State Killer case, was briefed by a colleague on a new method used to identify a New Hampshire serial murder. Terry Rasmussen, who died in 2010, had been tied to the Bear Brook Murders through the DNA of one of the still-unidentified victims. That victim turned out to be his biological child. Detectives then took the DNA profile of a little girl Rasmussen abandoned in 1986 and uploaded it to a genealogy website. The investigators hoped to pinpoint living relatives of the girl, thus providing her with an identity. In addition to finding her biological family, detectives discovered she was the biological daughter of a still-missing woman, Denise Beaudin. Beaudin was last seen with Rasmussen in 1981.5,6

From a genealogical perspective the methods used in solving these cases are instructive. The detectives in the DeAngelo case apparently used DNA evidence left at the scene of one of his crimes and entered it into a database at the websitesite This site allows users to upload the results of their DNA tests and compare them to the thousands of user-submitted genetic profiles they have on file. It is also the same tool that helped break the Bear Brook case. Detective Holes found several profiles indicating distant genetic matches with the DNA of the Golden State Killer*. The detective and his team then began the task of methodically developing family trees with traditional genealogical tools like the census, vital records, newspaper archives, etc. This allowed the team to trace the family histories of the people whose genetic profiles had shown a familial relationship with the killer. After finding the common ancestor these people shared, detectives began working forward in time, tracing every branch and stem that had grown out of those shared relatives.7 The technique of tracing a family from a common kinsman to the present day is used by forensic genealogists to find missing heirs for probate cases and other legal affairs. After identifying an age-appropriate male in the over two dozen family trees they created, law enforcement then surreptitiously collected a sample of his DNA from discarded trash. DNA testing from this sample provided a match with the genetic material of the killer, 72 year old DeAngelo, who was then arrested.8

Practices and theories in genetics have long been apart of many disciplines and modern advancements in the science have paired DNA analysis with other areas of expertise. From its early, rudimentary uses in plant and animal breeding to its combining of law enforcement and family history research today, DNA promises to find its way into more fields in the future.9 This newest teaming of genetics, detective work and genealogical practices made for a perfect storm to take down a monster.

Stay tuned for Part 2 where the discussion will focus on ethics and privacy concerns as they relate to the topic of genetic genealogy and its application use by law enforcement.



1 Flanagin, Jake. "How 'true crime' went from guilty pleasure to high culture," ( published 5 January 2016: last accessed 3 May 2018), paragraphs 1 through 8.
2 Farr, Christina. "As at home DNA tests become more common, people must grapple with surprises about their parents," ( published 10 December 2017: updated 11 December 2017: last accessed 3 May 2018), paragraphs 1 through 32.
3 Doe, George. "With genetic testing, I gave my parents the gift of divorce," ( published 9 September 2017: last accessed 3 May 2018), paragraphs 1 through 18.
4 Jouvenal, Justin . "To find alleged Golden State Killer, investigators first found his great-great-great-grandparents," ( published 30 April 2018: last accessed 3 May 2018), article.
5 Augenstein, Seth. "True ID of ‘Chameleon’ Killer Revealed: Terry Peder Rasmussen," ( published 18 August 2017: last accessed 3 May 2018), article.

6 Ibid.

7 Ho, Catherine. "Investigator who used DNA database to catch Golden State Killer suspect will write a book," ( published 2 May 2018: last accessed 3 May 2018), paragraph 1.
8 Ibid.
9 Winchester, A.M. "Genetics," ( published 18 August 2017: last accessed 3 May 2018), article.

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